1. Field of the Invention
The present invention relates to an engine, and more particularly to an engine used for automobiles, which is capable of discharging the working gases after purification, and which is capable of strengthening the engine brake.
2. Description of the Prior Art
It is known that exhaust gases discharged from automobiles contaminate air and provide public hazards. However it is unavoidable to some extent to discharge gases containing impurities hazardous to human health under the known automobile engines because of the fact that no effective device is equipped for purifying the gases before discharging from the cylinders.
When the automobile runs down a slope it is customary to minimize the speed of the engine so as to transmit the rotation of the wheels to the engine, thereby slowing down the rotation of the wheels. This prevents the brake shoes from becoming overheated owing to the tight contact with the wheels.
Herein this braking method will be referred to as engine brake. Under the known automobile engine systems the engine brake is effected by reducing the rotating speed of the engine but often it is not sufficient to brake the car. However there is a case where a strong engine brake must be effected.